package com.hummer.browser.pool.util;

import java.io.Closeable;
import java.util.NoSuchElementException;

import org.apache.commons.pool2.PooledObjectFactory;
import org.apache.commons.pool2.impl.GenericObjectPool;
import org.apache.commons.pool2.impl.GenericObjectPoolConfig;

import com.hummer.browser.exception.BrowserConnectionException;
import com.hummer.browser.exception.BrowserException;
import com.hummer.browser.exception.BrowserExhaustedPoolException;

public abstract class Pool<T> implements Closeable {
	  protected GenericObjectPool<T> internalPool;
	  
	  public Pool() {
	  }

	  public Pool(final GenericObjectPoolConfig poolConfig, PooledObjectFactory<T> factory) {
	    initPool(poolConfig, factory);
	  }

	  public void close() {
	    destroy();
	  }

	  public boolean isClosed() {
	    return this.internalPool.isClosed();
	  }

	  public void initPool(final GenericObjectPoolConfig poolConfig, PooledObjectFactory<T> factory) {
	    if (this.internalPool != null) {
	      try {
	        closeInternalPool();
	      } catch (Exception e) {
	      }
	    }

	    this.internalPool = new GenericObjectPool<T>(factory, poolConfig);
	  }

	  public T getResource() {
	    try {
	      return internalPool.borrowObject();
	    } catch (NoSuchElementException nse) {
	      if (null == nse.getCause()) { // The exception was caused by an exhausted pool
	        throw new BrowserExhaustedPoolException(
	            "Could not get a resource since the pool is exhausted", nse);
	      }
	      // Otherwise, the exception was caused by the implemented activateObject() or ValidateObject()
	      throw new BrowserException("Could not get a resource from the pool", nse);
	    } catch (Exception e) {
	      throw new BrowserConnectionException("Could not get a resource from the pool", e);
	    }
	  }

	  protected void returnResourceObject(final T resource) {
	    if (resource == null) {
	      return;
	    }
	    try {
	      internalPool.returnObject(resource);
	    } catch (Exception e) {
	      throw new BrowserException("Could not return the resource to the pool", e);
	    }
	  }

	  protected void returnBrokenResource(final T resource) {
	    if (resource != null) {
	      returnBrokenResourceObject(resource);
	    }
	  }

	  protected void returnResource(final T resource) {
	    if (resource != null) {
	      returnResourceObject(resource);
	    }
	  }

	  public void destroy() {
	    closeInternalPool();
	  }

	  protected void returnBrokenResourceObject(final T resource) {
	    try {
	      internalPool.invalidateObject(resource);
	    } catch (Exception e) {
	      throw new BrowserException("Could not return the broken resource to the pool", e);
	    }
	  }

	  protected void closeInternalPool() {
	    try {
	      internalPool.close();
	    } catch (Exception e) {
	      throw new BrowserException("Could not destroy the pool", e);
	    }
	  }
	  
	  /**
	   * Returns the number of instances currently borrowed from this pool.
	   *
	   * @return The number of instances currently borrowed from this pool, -1 if
	   * the pool is inactive.
	   */
	  public int getNumActive() {
	    if (poolInactive()) {
	      return -1;
	    }

	    return this.internalPool.getNumActive();
	  }
	  
	  /**
	   * Returns the number of instances currently idle in this pool.
	   *
	   * @return The number of instances currently idle in this pool, -1 if the
	   * pool is inactive.
	   */
	  public int getNumIdle() {
	    if (poolInactive()) {
	      return -1;
	    }

	    return this.internalPool.getNumIdle();
	  }
	  
	  /**
	   * Returns an estimate of the number of threads currently blocked waiting for
	   * a resource from this pool.
	   *
	   * @return The number of threads waiting, -1 if the pool is inactive.
	   */
	  public int getNumWaiters() {
	    if (poolInactive()) {
	      return -1;
	    }

	    return this.internalPool.getNumWaiters();
	  }
	  
	  /**
	   * Returns the mean waiting time spent by threads to obtain a resource from
	   * this pool.
	   *
	   * @return The mean waiting time, in milliseconds, -1 if the pool is
	   * inactive.
	   */
	  public long getMeanBorrowWaitTimeMillis() {
	    if (poolInactive()) {
	      return -1;
	    }

	    return this.internalPool.getMeanBorrowWaitTimeMillis();
	  }
	  
	  /**
	   * Returns the maximum waiting time spent by threads to obtain a resource
	   * from this pool.
	   *
	   * @return The maximum waiting time, in milliseconds, -1 if the pool is
	   * inactive.
	   */
	  public long getMaxBorrowWaitTimeMillis() {
	    if (poolInactive()) {
	      return -1;
	    }

	    return this.internalPool.getMaxBorrowWaitTimeMillis();
	  }

	  private boolean poolInactive() {
	    return this.internalPool == null || this.internalPool.isClosed();
	  }

	  public void addObjects(int count) {
	    try {
	      for (int i = 0; i < count; i++) {
	        this.internalPool.addObject();
	      }
	    } catch (Exception e) {
	      throw new BrowserException("Error trying to add idle objects", e);
	    }
	  }
	}